1. Field of the Invention
This invention relates to processes and apparatus for producing steam from a hydrothermal flow and for utilizing such steam. It further relates to the production of mechanical energy from such steam and from the thermal energy contained in a two-phase hydrothermal flow, especially with respect to two-phase flows of steam and water which occur in industrial processes and those which occur below and/or above the earth's surface in the operation of wells drawing from subterranean water dominated geothermal resources. It also relates to the control of environmental pollution in the utilization of hydrothermal flows containing gaseous contaminants.
2. Description of the Prior Art
The utilization of thermal energy available in a flow of steam and water to produce mechanical power has been accomplished by separating the two phases and then passing the steam through a prime mover, e.g. a steam driven turbine. Thermal energy available in the form of sensible heat contained in hot liquid water has been converted into steam which in turn has been used to produce mechanical energy by flashing at a reduced pressure or by transferring such energy in a boiler from the hot water to other water maintained at a temperature and pressure considerably lower than the temperature and vapor pressure of the hot water, and the low pressure steams so generated have been utilized to drive a relatively poor efficiency prime mover capable of operating at such low pressure. Also, sensible heat energy contained in hot water has been converted into mechanical energy by use of the so called binary system by which sensible heat is employed to boil a fluid other than water which has a lower boiling point than water, e.g. an organic fluid, and the vaporized fluid generated at a relatively high pressure thereby is circulated through a separate turbine and condenser in a closed loop. These practices with respect to two-phase hydrothermal flows have either utilized thermal energy only from the steam phase or have required the use of special combinations of high and low pressure steam driven prime movers or special aggregations of separate power producing systems, e.g. one based on conventional steam utilization and another employing the binary system, all at considerable additional capital cost and operating expense per unit of mechanical power produced.
The utilization of the thermal energy available in two-phase hydrothermal fluids from geothermal resources has generally been subjected to environmental and economic problems associated with the gases which contaminate the steam separated from the two-phase flow. Such gases result from flashing at the lower than subterranean pressures which the fluids experience in rising to the earth's surface and in being prepared for utilization. Some of these gases, e.g. hydrogen sulfide, are pollutants to the environment and often special facilities directed to control the emission of one or more specific contaminants are required. Other substances present in the steam, e.g. boric acid and silica, deposit scaling materials in the power production equipment and are responsible for costly periodic maintanance practices.